In general, the art involving electrically operated valves for handling pressurized gases is highly developed and a large number of designs have been known for many years and have long been in successful operation. Many competing designs are available in the marketplace and such designs have been successfully modified for application to a wide variety of specific uses. This art has, however, developed primarily in connection with relatively large valves, such as valves adapted for connection to conduits of at least about 1/4 inch internal diameter (1/8 NPT pipe) and arranged for supplying, for example, air cylinders of one inch in diameter and having a stroke of up to 8 inches.
However, in addition to the foregoing, there has over the past several years been developing a series of applications for electrically operated valves for controlling a pressurized gas which valves are extremely small.
In some instances such small valves are intended for controlling correspondingly small pressure responsive cylinders and in other cases such small valves are to be provided insofar as possible with the flow characteristics of larger valves and intended for controlling pressure responsive cylinders of the sizes above mentioned. These last named valves present a wholly different series of problems in that the concepts and resulting designs developed with respect to large valves become wholly inappropriate when applied to small valves. These problems develop at several points, partly with respect to tolerances, partly with respect to access for machine operations and partly with respect to various functional aspects.
Such problems in the design of small valves occur both in the design of control valves as for locating in a control panel for controlling a plurality of working valves on a machine tool or as in the designing of such working valves themselves where it is desirable to reduce their size as much as possible for a variety of purposes including economy of space required and economy of working fluid absorbed by the valve.
Among such problems and particularly a problem which has existed for many years with conventional poppet valves, is the unbalanced force which is imposed on the valve stem by the pressurized gas. In most conventional poppet valves, the valve stem has one end thereof extending outwardly of the housing and connected to an operator, whereas the other end of the valve stem terminates within the valve housing and is exposed to the pressure fluid. In such case, regardless of whether the valve is normally open or normally closed, it has usually been necessary to utilize springs in opposition to the pressure unbalance in order to enable the valve to respond properly to whatever control force is applied thereto. However, when spring pressure is utilized, this presents difficulties in applying a single valve to meet a wide range of pressure situations. Thus, it has often been necessary to change the spring depending upon the pressure of the fluid being utilized, but this itself is undesirable and creates additional manufacturing and maintenance problems. In some prior poppet valves, springs have not been utilized to overcome the pressure unbalance on the valve, but instead the orifice between the valve and the valve seat is designed to accommodate only a limited pressure range so that a valve having a relatively large orifice will be limited to low pressure valves whereas a valve having a small orifice will be capable of handling higher pressures. Needless to say, valve structures of this type are also undesirable inasmuch as a single valve again is not able to meet a wide range of pressure situations.
These problems become especially severe when applied to the valves of small sizes. In some cases, the space occupied by such balance springs, when same are used, undesirably limits the extent to which the valve size can be reduced. In other cases the forces to be balanced in small valves are difficult to hold within acceptable tolerances for balancing by springs. In those situations where orifice control is utilized as above-mentioned, this, for reasons of sizes and tolerances, becomes extremely difficult to apply to small valves and hence is often not feasible.
Accordingly, the objects of the invention include:
1. To provide a poppet valve for controlling the flow of a pressurized gas, which valve will be efficient and reliable and can be economically manufactured in very small sizes.
2. To provide a valve, as aforesaid, which when produced in the very small sizes indicated will still be sturdy and reliable over a long period of time of high speed repetitive operation.
3. To provide a valve, as aforesaid, which in spite of the very small size can be efficiently associated with conduits as normally used for large valves.
4. To provide a valve, as aforesaid, which in spite of the very small size will have performance characteristics as good as or better than those associated with previously known larger valves and can, accordingly, be used effectively as a working valve for supplying pressure fluid cylinders of sizes more normally associated with control by larger valves.
5. To provide a valve, as aforesaid, wherein the fluid pressure is not permitted to impose any substantial unbalance on the valve stem so that a single valve can be made to operate effectively over a wide pressure range.
6. To provide a valve, as aforesaid, wherein the valve stem extends outwardly from the opposite ends of the housing and has a seal ring surrounding same and engaging a valve seat in the manner of a poppet valve, with opposite ends of the valve stem being sealed with respect to the valve housing to prevent pressure fluid from imposing an unbalanced pressure force on the ends of the valve stem.
7. To provide a valve, as aforesaid, in which all fliud lines thereto connect therewith at only one end of said valve whereby to make possible a convenient and neat connection of said valve into a fluid pressure system.
Other objects and purposes of the invention will be apparent upon examination of the accompanying drawings and reading of the following specification.